Coded track circuits for railroads



Aug. 7, 1945. N. B. coLEY CODED TRACK CIRCUIT FOR RAILROADS Fiied Nov. 19, 1942 INVENTOR 7L, f2.

ATINEY Legg o mw Il l! @Ecuao op van llll Adi Patented ug. 7, 1945 CODED TRACK CIRCUITS FOR RAILROADS `Nelson B. Coley, Rochester, N 1.' Y., assignor to General Railway Signal Company, Rochester,`

Application November 19, 1942, Serial No. 466,150

` claims. (oi. 2461-34) Thepresent invention relates to track circuits of the coded type `and more particularly of the driven-inverse type where driven impulses and inverse impulses of current are alternately transnitted in opposite direction through a track sec ion. f Since the code transmitting apparatus for transmitting the driven code is located atthe same end of the section where the receiving apparatus for the inverse code is located great care must be exercised to prevent `this driven coding apparatus from actuating the inverse code` re*- ceiving apparatus. Not only is' it important that current from the driven code track source shall not be able to directly reach the inverse code re 'ceiving apparatus but also shall lnot be able to reach it as an electrolytio or a condenser discharge (rails in multiple constituting a condenser or theballast `electrolytic, action constitutingan ineiiicient battery) nor as an inductive kick from an inductive circuit, such as the track circuit.

In accordance with the present invention it is proposed to connect an inductive translating device directly and permanently across` the track rails 4at. the end where the driven coding apparatus is located and where the inverse'code following track relay is located to momentarily store an inverse code impuse When one is received and to later retransmit the impulse to the code "following vinverse track relay, and .to serve as a continuous shunt' for shunting away current from a yforeign source when present. This `translating device by being directly and continou'sly confnected across the track rails is also capable of aby` sorbingfeedV back from the track circuit due to condensive or electrolytic actionand is also able to counteract the inductive kick of the track circuit. translating device to the code following inverse track relay only when the coding contactconstituting part of the apparatus for transmitting the driven code has been fully opened in order to prevent self-coding of the inverse code receiving-apparatus by the driven coding apparatus located at the same end of the section. An object of the present invention thus resides in the con# struction of a coded track circuit wherein the presence of a train may be definitely and reliably manifested at both ends of the section in which such track circuit .is located. s

More specifically it is proposed to have this translating device constitute a transformer,although some other form of translating device such asa polarity responsive relay may be employed if desired, this transformer having its pri- It is proposed to operatively connectvthis mary winding directly and continuously l connected across the track rails and having its sec-` ondary winding 'intermittently connected to an inverse code following track relay only during periods ,when the coding Contact for applying `the driven code is open. .f l Other objects,v purposes and characteristic features of the present invention` will be more specifically pointed out in the specication hereinafter andvwill be obvious when this specification is read in connection with the drawing in which-f Fig. l illustrates conventionally one embodif ment of the invention; l

Fig. 2 illustrates a time chart through themedium'of which the sequence of operation of the devices contstituting the apparatus throughout one complete cycle may be ascertained; and Figs. 3, 4 and 5 illustrate sources of foreign' current that may be tolerated across-the track rails without the reception of a false and unauthorized inverse code. t. Structure.-Referring to Fig. 1 of the drawing a section or block M of a railway'track'including track rails I0 has been divided from the remaining track by insulating joints ||\,1over which section or block M traiiic presumably travels; from left to` right as indicated by thearrow l2. At the entrance or left end of thelblocky M;

' which may also be called the drivencode retrolled by the track repeated yrelay TRP and the code following track relay TR.` through contacts I1 and i8 of these respective relays.

A transformer T is also employed at the. en:- trance end to the block M for the purpose of creating inverse code impulses upon dropping of the track repeater relayv TRP through the medium of Contact 20 of this trackrepeater relay TRP, `such inverse track impulse being applied to the track only in the event the inverse code applying relay ICAR, is then energized to` hold `its front contact 2| closed, and then onlyv if the track repeater relay TRPP is then assuming its ener-V gized position and is holding its front AcontactiZZ closed. It should be observed from the conventional showing illustrated that the track relay TR is a relay of the polar type which is biased to the left-hand position by a biasing spring 24. The track repeater relays TRP and TRPP are, however, rather quick acting neutral relays as conventionally illustrated. It is readily understood from the apparatus thus far described that intermittent operation of the track relay TR to its energized and biased position alternately will result in momentary picking up of the relays TRP and TRPP in succession, it being understood that the second repeater relay TRPP is energized only during the drop-away period of the track repeater relay TRP. A dottedarrow 25 has been shown adjacent the secondary winding of the inverse code transformer T and it should be understood that this dotted arrow illustrates the direction in which voltage is induced in the secondary winding upon the opening of the primary winding at the front contact 20 of the track repea-ter relay TRP. Since it is the dropping of the track repeater relay TRP whichy causes deenergi'zati'onof the second tracky repeater relay TRPP it will beobserved that the circuit for the primary winding of the transformer T is broken when the contact 22 of the relay TRPP still assumes its raised position so that the inductive k-ick due to the breaking of the energizing circuit of 'the primary winding and induced in the secondary winding of the transformer T may iiow through thefront contact 22 of thesecondtrack repeater relay TRPP and into the track circuit during the drop-away period of the relay TRPP. This relationship of operation of the devices at the entrance -end to the track section M should be borne in mindv when the operation of the system isl considered hereinafter.

"Let us now refer to the exit end or right-hand end of the track section or block, which for convenience may be called the driven code transmittingand inverse code receiving end ofthe section. At this exit end of the track section M there is provided a code repeating relay CPR which intermittently picks up and drops its contacts to characterize a `code which may be of a high or a low rate depending upon traiiic conditions inr advance. This code repeating relay CPR may be directlycontrolled by a coder or may repeat the code received at the adjacent end of the track section in advance. A front contact 21 of this code repeating relay CPR is connected in series with thetrack battery 'I'B and a series resistance rl across the track rails I0 at thiseast or exit end of the track section and so that intermittent picking up of this code repeater relay CPR through the medium of its front contact 21 applies impulses of a driven code to this end of the track section. The inverse code receiving translating device ICT, which in the form illustrated constitutes a transformer, is directly and xedly connected across the track rails with a series resistance* r2 included in series therewith. Obviously, 'the resistance of the primary winding of the transformer ICT may be made high enough and the resistance r2 omitted.

' One-y reason forconnecting the inverse code receiving translating device directlyv across the track rails is to provide a continuous drainage path fora foreign source of potential which may bel accidentally present across the track rails due to some unauthorized or foreign source. The outgoing circuit of this translating device ICT, which in" the form illustrated comprises the secondary winding of a transformer, is connected through the medium of back contacts 28 and 29 of the code repeater relay CPR to the input circuit of the inverse code following track relay ITR. It will be observed by the `conventional showing illustrated that this inverse code following track relay ITR is one of the polar mag-stick type, that is, is a relay which will remain in its last operated position until changed by reason of an internal permanent magnet and which is operated to one position if current of one polarity is applied thereto and is f operated to another position if current of another polarity is applied thereto.

When the contacts 28 and 29 of the code repeating relay CPR assume their energized or raised position the winding of the inverse code following track relay ITR is connected to a local battery B so that the inverse code following track relay ITR is returned to its normal position upon each energization of the code repeater relay CPR, this inverse code track relay ITR being operated to its actuated left-hand position each time the code repeating relay CPR assumes its deenergized position provided there is then induced in the secondary winding of the inverse code transformer ICT a voltage of the proper magnitude and polarity.

In order to manifest by a continuously closed contact the fact that an inverse multiple element code is being received the front and back track repeater relays FP and FBP have been provided. It will be observed that the front repeater relay FP is energized through a circuit closed when the contact 3|)l of the inverse code following track relay ITR assumes its left-hand or actuated posi'- tin whereas a circuit for the front-back repeater relay FBP includes the contact 30 of the inverse track relay ITR assuming its right-hand position and the front contact 3| of the front repeater relay FP'. The reception of an inverse code is therefore manifested by the closed condition of front contact 32 of the front-back repeater relay FBP, and this front contact 32 cannot be closed unless the relay ITR is operated to its two positions alternately.

It should be observed that a downwardly directed dotted arrow 35 has been illustrated adjacent the primary winding of the translating de'- vice or inverse code transformer ICT. This is to signify thatl an increase in current in a downwardly direction, and consequently a decreasing upwardly directed current, will induce a current in thesecondary winding of this Itransformer ICT which, if of sufficient magnitude and with back contacts 28 and 29 of code repeater relay CPR lthen closed, will cause the inverse code following track relay ITR to be actuated to its left-hand position. It should alsov be noted that vclosure of front contact 21 of the code repeating relay CPR will cause such an increase in downwardly flowing current in the primary winding of the transformer ICT. This increase of flow of current in the direction of the arrow 35 although it induces a voltage in the secondary winding of this transformer of the proper polarity to actuate the inverse code following track relay ITR, will not actuate this relay because the back contacts 28 and 29 of `the relay CPR included in the circuit of the inverse code following track relay ITR is then open.

OperatiofrL.-In order .to briefly and concisely set forth the successive steps of operation of the various devices illustrated in Fig. 1 during one cycle of operation of the combined driven and inverse code track circuited section Fig. 2 of the drawing has been provided. This Fig. 2 illus'- trates the varioussteps in one cycle of operation of the system and their sequence. `That is, Fig. 2 may be consideredy to be a brief recitation of an operating cycle of the system or may, if desired, be considered rto be a time chart illustrating the operation of the various devices in which the column' ftime illustrates the lapse of time through the cycle.

With the various devices assuming the position illustrated in'rfig. 1 of the drawing, which is merely a transitory position of the apparatus during the transmission of both a driven and an inverse code, and if the time cycle be divided into nine parts, as illustrated in the column designated time shown at the extreme left in Fig. 2 of thel drawing, the operation of certain devices in each of these 9 time elements may be readily observed from Fig. A2 of the drawing. Referring to Figs. l and 2 it will be observed from Fig. 1 that the relay TRPP `is shown deenergized but is also shown assuming its energized position. In other words, the relay TRPP` is in a transitory condition and is about to assume its deenergized position because it is' already deenergized. In other words, during the iirst time elementl illustrated in Fig. 2 the relay TRPP goes down, because the relay TRP controlling it is already down and has broken the energizing circuit of this secondary repeater relay TRPP. During the second time interval the code repeating relay CPR, which is driven by suitable oscillatory or` other code creating apparatus either directly or repeated through the track circuit in advance, picks up to apply a driven code to the right- `hand or exit end of the block M. During the third interval this driven code impulse ilows through the track rails and operates the track relay TR located at the opposite end ofthe block M to its right-hand actuated position.` Simultaneously with the now of current through the front Contact 2l of the code repeating relay CPR to the track relay TR current may also flow from the battery B through the front contacts 28 and 29 of this same code repeating relay CPR to result in the actuation of the inverse code track relay ITR back to its right-hand dotted position, and furthermore, the closure of front contact 2l of the code repeating relay CPR not only applies a driven code impulse to the track circuit to actuate the track relay TR but also applies a momentary impulse of current in a downward direction through the primary winding of the inverse code transformer ICT which current il-ows in a polar direction -as` indicated by the dotted arrow 35. Although this impulse of current in the primary winding of the transformer ICT is in the proper polar direction to induce a current in the secondary winding of the transformer ICT in the proper direction to operate the inverse code track relay ITR to its left-hand active position, this current cannot flow because the back contacts 28 and 29 of the code repeating relay CPR are now open.

During the next or fourth time period illustrated in Fig. 2 the track repeater relay TRP is picked up and at its front contact 26 energizes the transformer T. This is of no particular consequence at the present time because the secondary winding of this transformer Tis now open at front contact 22 ofil the secondary track repeater relay TRPP. During the fth time interval illustrated in Fig. 2 of the drawing the code repeating relayCPR at the exit end of the block M assumes its deenergized position thereby causing a sudden inductive kickin the primary winding of the transformer ICT, that is the downward ilow of current through the primary Winding of transformer ICT continues but gradually decreases in spite of the opening of the front contact 21 of the relay CPR and this inverse kick causes a sharp cut-off of the current constituting the driven code impulse in the track rails. When the code repeating relay CPR has fully assumed its deenergized position an induced voltage ofv a polarity to actuate the inverse track relay ITR to the right is induced in the secondary winding of the transformer ICT and will ow to the inverse track relay ITR, but since this kick is due to decrease in downwardly flowing current in the primary winding of the transformer ICT this induced voltage is of a polarity to actuate the inverse code track relay ITR to its right-hand position, which it already assumes, so that no harm is done and no actuation takes place. It may however be pointed out that if the battery B were omitted this induced voltage could be used to return the relay ITR to its right-hand nonactuated position.

During the sixth interval of time illustrated in Fig. 2 of the drawing the track relay TR is actuated to its left-hand position by its spring 24. During the seventh interval of time of the cycle as illustrated in Fig. 2 of the drawing the second track repeater relay TRPP is picked up due to closure of the left-hand contact lll of the track relay TR with the track repeater relay TRP still assuming its energized position, namely, through the contact I8 in its left-hand position and through a front contact l1 of this track repeater relay TRP. During the eighth interval of time, and primarily due to operation of the track relay TR back to its normal left-hand position, the track repeater relay TRP assumes its deenergized position and by the opening of its A front contact 2li deenergizes the transformer T.

This causes a current to be induced in the secondaly winding of this transformer T in a direction as indicated by the dotted arrow 25 thereby transmitting an inverse code impulse through the track rails from the entering end to the exit end of the block M which results in the increase of a downwardly flowing current through thepriw mary winding of the transformer ICT at the exit end at a time when the back contacts 28 and 29 of the code repeating relay CPR are closed. Since the voltage induced in the secondary winding of the transformer ICT is now of the proper polarity to actuate the inverse track relay ITR to its left-hand position at a time when these back contacts 28 and 29 are closed the inverse code track relay ITR is actuated to its left-hand actuated position. All of the devices illustrated in Fig. l of the drawing have now been returned to the positions in which they are illustrated, so that a complete cycle ofl operation of the system has been reviewed.

It will of course be understood that these cycles are repeated and that intermittent operation of the contact 3E of the inverse code following track relay ITR causes the front repeater relay FP and the front-back repeater relay FBP to both assume their energized position continuously, because they are slow dropping to `an extent to remain up between successive impulses applied by contact 30. This results in thepermanent closure of front contact 320i relay FBP. Likewise intermittent energization of the second track repeater relay 'I'RPP and intermittent closure of its front contact I6 will apply impulses of current to the decoding apparatus D to result in the op eration of lthe signal S to its clear or caution position depending upon whether a clear code or a caution code was then transmitted by the code repeating relay CPR.

Provision against self-coding from foreign sources-Let us now observe whether the presence of a false or unauthorized foreign source of direct current potential across the track rails can cause false coding of the inverse track relay I'IR by the operation of the contacts of the code repeating relay CPR. Let us first assume that a foreign source FBI of direct current potential of such potential and polarity as illustrated in Fig. 3 of the drawing is present across the track rails at a point as indicated by the dotted lead lines 31 (see Fig. 1). It will be observed that this foreign source of potential is included in series with the track battery TB each time the contact 21 of the code repeating relay CPR is closed with the two sources of current in the local circuit poled in the same direction, that is, with their voltages cumulative. The presence of such a foreign source of potential would probably prevent sufficient current reaching the track relay TR so that functioning of the main track circuit transmitting the driven code impulses would cease. Furthermore, this foreign source of current FBI could not produce an unauthorized inverse impulse for the inverse track relay I'IR because this foreign source of potential FBI would, if anything, cause current to flow in the primary winding of the transformer ICT in the wrong direction and therefore not create an effective impulse. In other words, the presence of a foreign source of potential such as indicated in Fig. 3 of the drawing and connected across the track rails as indicated by the lead lines 31 would cause an vincreasing upwardly flowing current in the primary winding of transformer ICT and could not possibly causev the false and improper coding of the inverse track relay ITR. The same results would occur if the source FBI were of a higher potential.

Let us now assume that a similar foreign source of potential FB2 but of opposite polarity and as indicated in Fig. 4 is applied vacross the track lrails at the l'dotted lead wires 31. It is assumed that this foreign source of potential FB2 is of a polarity to buck or oppose the potential of the track battery TB in the local circuit including these two batteries in multiple and that it is of a `potential commensurate to or less than the voltage of the track battery TB. This foreign source of potential would cause an increase in the flow of current through the track relayTR while the coding contact 21 is closed but upon opening of this Contact 21 will not allow vthis current to fall to zero as a result of Which a track relay TRA may remain in its energized position continuously and thereby prevent the clearing of the signal S. This foreign source of potential FB2 would not cause false coding of the inverse track relay ITRl because the arrangement would constitute the presence of two batteries in multiple across the track rails of substantially the same potential of which one battery is intermittently disconnected from the rails whereas the other one is not as a result of which each openingof the contact 21 of the code repeating relay CPR would causea reduction in the downwardly owing crrent in the primary winding of the transformer ICT, and this reduction in current would occur at a time when 'the back contacts '28 and 29 are closed and would,

if anything, cause operationof the inverse track relay ITR to its vright-hand position, Since the right-hand position is the non-actuated position n'ol harm could be done by such an impulse impressed on the winding of the inverse code following relay ITR.

Let us now assume that there is a foreign source of current of the same polarity present as just discussed and as conventionally illustrated in Fig. 4 by the battery FB2 but of a greater potential than that of the Atrack battery TB. Let us assume this foreign source FBS to be present at the point of the dotted 1eadin wires 31. The presence of this source of foreign potential F133 would cause a substantial amount of current to now in a downward direction through the primary winding of the inverse transformer ICT at all times and this current would be momentarily reduced each time that the front Contact 21 of the code repeating relay CPR is closed. This is true because the source FB3 would charge the battery 'I'B while the contact 21 is closed. In other words, upon opening of this contact 21 of the code repeating relay CPR an increase in the downwarly flowing current in the primary winding of the transformer ICT would occur at a time when the contacts 28 and 29 of the code repeater relay are closedl to connect the secondary Winding of this transformer ICT to the Winding of the inverse track relay ITR. At rst hand it would appear that false coding of the inverse track relay ITR due to intermittent picking up and dropping of the code repeating relay CPR would occur with a high voltage'source of potential poled in a direction as indicated in Fig. 5 and present between the rails of the track section. Such falsev coding of the inverse track relay ITR does, however, not occur because the inverse code transformer ICT is Vdesigned to be substantially fully magnetically saturated as a result of a foreign source o'ffcurrent of such polarity as conventionally indicated in Fig. 5 of the drawing, especially if the `voltage of this source is equal to or in excess of the voltage of the track battery TB. Obviously, if the core of the transformer ICT is very highly saturated with the contact 21 of the code repeating relay CPR either closed or open subsequent intermittent opening and closing of 4this contact 21 will induce substantially no -potential in the secondary winding of this transformer ICT because the magnetic density in the core of the transformer does not materially change in response to such intermittent opening and closing of `this contact 21 of the relay CP-R.

The applicant has thus devised a track circuit arrangement which transmits driven and inverse code impulses alternately in opposite directions to ymaintain code responsive apparatus energized vat both ends of fthe section during nonoccupancy'of the section and this apparatus is of a construction so that the rpresence of a train on the track sectionwill be definitely yand positively manifested at both ends of the section. `In other words, the applicant has provided a system in which the inverse code may be relied upon to manifest at ythe exit end of the section the fact that the section is not occupied.

Having thus shown and described one specific embodiment of the present inventionfand having illustratedonly one specic form of apparatus for `performing the functions of the present invention it is -desired to be understood that various alternative devices may be employed in practising the invention depending on local conditions and 'that various changes, modifications -and ad- Without departing from vthe spirit or scope thereof except as demanded by the scope of the appended claims.

What is claimed as new is:

. 1. In adriven-inverse coded track circuit of the check inverse code type; the combination with a driven coded track circuit including the rails of a section, a driving source of current and a coding contact at one end of the section for creating a driven code and a code following track relay at the other end of the section for responding to such driven code; and an inverse coded track circuit including the same track rails, and including an inverse coding contact for applying inverse code impulses from an inverse source of current located at said other end of said section between the impulses of said driven code, a transformer having a primary and a secondary winding and having its primary winding connected across the track rails permanently, a polar inverse code following track relay which remains in its last operated position when deenergized and which is operated in one direction in response to an inverse code impulse derived from the secondary winding of said transformer and is disconnected from said secondary winding and is operated in the other direction by means including a local source of current and a contact closed only `when said coding contact for creating a driven code is closed.

2. In adriven-inverse coded track circuit wherein driven and inverse current pulses are alternately transmitted in opposite directions through the track rails of a section having a driven code transmitting and inverse code receiving end and having a driven code receiving and an inverse code transmitting end; the combination with a section of track; a driven code transmitting and inverse code receiving end for said section including a coding contact having a source of current in series therewith and an inverse code receiving coil permanently connected across the track rails and in multiple with said contact and source in series and also including an inverse code following relay responsive to the energiazticn o-f said coil only after said coding contact is open; and

a driven code receiving and inverse code transmitting ,end for said section including a code following track relay, and means for transmitting an inverse code impulse. to the opposite end of said section after each energization and picking up of said code following track relay.

3. In a driven-inverse coded track circuit wherein driven and inverse current rpulses are alternately transmitted in opposite directions through the track rails of a section having a driven code transmitting and inverse code receiving end and having a driven code receiving and an inverse code transmitting end; the combination with a section of track; a driven code transmitting and inverse code receiving end for said section including a coding contact having a source of current in series therewith and an inverse code receiving transformer having its primary winding permanently connected across the track rails and in multiple with said contact and source in series and also including ank inverse code following relay responsive to the energization of said transformer only after said coding contact is open; and a driven code receiving and inverse code transmitting end for said'section including a code following track relay, and means for transmitting an inverse code pulse to the opposite end of said section after each energization and picking up of said code following track relay.

4. In a combined driven and inverse coded -track circuit; 'the combination with a section of track having an entrance end and an exit end; apparatus `including the trackrails of said section,.driven code creating means at the exit end 'ofsaid section fortransmitting a multiple impulse driven code from said exit end to said entrance `end .and multiple impulse code receiving means at said entrance end for Vreceiving and decoding said driven code; and apparatus including the same track rails and including means for creating inverse-.code impulses between the impulses of said driven code and transmitting them from said entrance end to said exit end and includ- :ing inverse code receiving means at said exit end comprising. a transformer having its primary winding connected directly and fixedly across the track rails and having its secondary winding connected to a 4polarity responsive mag-stick relay through the medium of a circuit having contacts thereinwhich are, closed when said driven code creating means does not transmit a driven code impulse and which wholly disconnects said magstick relay fromy said secondary windingl while said driven code creating means transmits a driven code impulse.

5. In a combined driven and inverse coded track circuit; the combination vwith a section of track having an entrance end and an exit end;`

apparatus including the track rails of said section, driven code creating means at the exit end of said section for transmitting a multiple impulse driven code from said exit end to said entrance end and multiple impulse code receiving means at said entrance end for receiving and decoding said driven code; and apparatus including the same track rails and including means for creating inverse code impulses between the impulses of said driven code and transmitting them from said entrance end to said exit end and including inverse code receiving means at said exit end `comprising a translating device having input and output wires and having its input wires connected directly and iixedly across the track rails and having its output wires connected to a polarity responsivemag-stick relay through the medium of a circuit having contacts therein which are closed when said driven code creating means does not transmit a driven code impulse and which wholly disconnects said relay from said translating device when said driven code creating means is transmitting a code impulse.

6. In a combined driven and inverse coded track circuit of the type described; the combination with a section of track having an entrance end and an exit end; apparatus at said entrance` end responsive to a multiple impulse driven code and including means for applying impulses of inverse code between the impulses of the driven code received; and of multiple impulse driven code creating means and multiple impulse inverse code receiving means at said exit end comprising, a track source, a transformer having its primary winding connected across the track rails permanently, coding contacts and a two-position mag-stick polar inverse track relay, and means for connecting one coding contact in series with said source and in turn in multiple with the primary winding of said transformer and across the track rails and for connecting said mag-stick relay to the secondary winding of said transformer through contacts closed when said one coding contact is open and for wholly disconnecting said mag-stick relay from said secondary winding when said one coding contact is closed.

7. In a 'combined driven and inverse coded track circuit of the type described; ithe combination with a section oi track havingr an entrance end and an exit end; apparatus at said entrance end responsive to a multiple impulse drivencode and including means for creating and applying impulses of inverse code between the impulses of the drivencode received; and of multiple impulse driven code creating means and multiple impulse inverse'code receivingmeans at said exit and comprising, a track source, a translating device having input and output Wiresvand having its input wires connected across thetrack rails permanently, coding contacts and a two-position mag-stick polar inverse track relay, and means Y for connecting one coding contact in series with said track source and the two in series in turn in multiple with the input wires of said translating device and for connecting said mag-stick relay to the output wires of saidtranslating device through contacts closed when said one coding contact is open and for Wholly disconnecting said mag-stick relay from said translating device when said one coding contact is closed.

i 8. In a combined driven and inverse `coded track circuit of the type described; the combination with a section of track having an entrance end and an exit end; apparatus at said entrance `end responsive to a multiple impulse driven code and including means for 'creating and applying impulses of inverse code between the impulses of the driven code received; and of multiple impulse driven code creating m'eans and multiple impulse inverse code receiving means at said exit end comprising, a track source, a local source, a transformer having a primary and a secondary winding and having its primary winding connected .across the track rails permanently, coding contacts and a two-position mag-stick polar inverse track relay, and means for connecting one coding contact in series with said track source and in turn in multiple with the primary winding of said transformer and across the track rails, for connecting said mag-stick relay to the secondary Winding of said transformer through contacts closed when said one coding contact is open, and for disconnecting said inverse track relay from said secondary winding and to said local source of current when said one codingcontact is closed.

9. In a combined driven and inverse coded track circuit of the type described; the combinay tion with a section of track having an entrance end and an exit end; apparatus at said entrance end responsive to a multiple impulse driven code and including means for creating and applying impulses of inverse code between the impulses of the driven code received; and of multiple impulse driven code creating means and multiple impulse inverse code receiving means at said exit end comprising, a track source, a local source, a translating device having input wires and output wires and having its input wires connected across the track rails permanently, coding contacts and a two-position mag-stick polar inverse track relay, and means for connecting one coding contact in series with said track source and the two in series in turn in multiple with the input wires of said translating device and across the track rails, ior connecting said mag-stick relay to the output wires of said translating device through contacts closed when said one coding contact is open, and for disconnecting said mag-stick relay from'said translating device and` to said local source of current when said one coding 4contact is closed.

10. In a combined driven and inverse coded track circuit `for transmitting driven and inverse codes alternately in opposite directions over the track rails of a track section; the combination with a track section; of code creating means at opposite ends of said track section for alternately transmitting driven code impulses in one direc rtion and inverse code impulses in opposite direction through the rails of said section; driven code receiving and decoding means at one end of said section for receiving and decoding said driven code; an `inverse code following track relay of the polar type at the other end of said section, a transformer having a primary winding connected directly and continuously across the rails of said section and having a secondary winding Afor operating said inverse code following track relay in one direction; and other means including said code creating means for wholly disconnecting said inverse code following relay from said secondary winding and for positively operating said inverse code following track relay in the opposite direction, whereby the primary winding of said transformer performs a continuous shunting function for shunting away current from a possible foreign source of direct current across said rails, and whereby said inverse code following track relay will not follow a code unless it is by positive actuation returned to its normal position after every code impulse.

l1. In a combined driven and inverse coded track circuit for transmitting driven and inverse direct current codes alternately in opposite directions over the track rails of a track section; the combination with a track section; of code creating means at opposite ends of said track section for alternately transmitting direct current driven code impulses in one direction and direct current inverse code impulses in the opposite direction through the rails of said section; direct 'current driven code receiving and decoding means at one end or said section for receiving and decoding said driven code; direct current inverse code receiving means at the other end of said section comprising a transformer and means for connecting its primary winding directly and continuously across the rails of said section and its secondary winding to a code following track relay during each 01TA period of said driven code but wholly disconnecting it from said secondary winding during each on period of said driven code, whereby the primary winding of said transformer performs a continuous shunting function forshunting away current from a possible foreign source of direct currentacross said rails; and a signal controlled by said driven code decoding means.

12. In a combined driven and inverse coded track circuit for transmitting driven and inverse codes of direct current impulses alternately in opposite directions over the track rails of a track section; the combination with a track section; of

code creating means at opposite ends of said track section for alternately transmitting direct current driven code impulses in one direction and direct current inverse code impulses in opposite direction and between the impulses of said driven -code through the rails of said section; direct current driven code receiving and decoding means at one end of said section for receiving and decoding saidr driven code; and direct current inverse code receiving means at the other end of said section Icomprising a transformer having a primary and a 'secondary winding and having its primary winding. connected directly and continuously across the rails of said section and having its secondary winding connected by said `driven code creating direct current codes alternately in opposite directions over the track rails of a track section; the combination with a track section; of code creating means at opposite ends of said track section for alternately transmitting driven direct current code impulses in one direction and inverse direct current code impulses in the opposite direction through the rails of said section; driven direct current code receiving and decoding means at one end of said section for receiving and decoding said driven direct current code; inverse direct current code receiving means at the other end of said section comprising a transformer having a primary winding and a secondary winding and having its primary winding connected directly `and continuously across the rails of said section and having` its secondary winding connected to a direct current code following track relay during each off period of said driven code by said driven code creating means and having its secondary winding wholly disconnected from said code following track relay during on periods of said driven code by said driven code creating means; whereby the primary winding of said transformer performs a continuous shunting function for shunting away current from a possible foreign source 'of direct current across said rails; and electro-responsive means controlled by said code following track relay.

14. In a coded track circuit, the combination with a track section, a two position polar relay constructed to be operated to one position when its winding is energized by current of one polarity to be operated to the other position when its winding is energized by current of the opposite polarity and to remain in its last operated position when dcenergized, a transformer having one winding connected continuously across the track rails of said section and having another winding connected to said polar relay once for each impulse of a code transmitted over said track section and effective to energize said relay with current of one polarity, and means for wholly disconnecting said polar relay from said transformer and then energizing said polar relay with current of the opposite polarity from a local source of current during each off period between two impulses of such code.

15. In a coded track circuit, the combination with a track section, a track relay, a repeater track relay, a repeater track repeater relay, a transformer having a primary winding and a secondary winding, contacts on said repeater track repeater relay for alternately connecting the secondary winding of said transformer and said track relay -to said track section as said repeater track repeater relay assumes one and the other of its two positions, a circuit for said primary winding of said transformer including a source of direct current and a first contact of said repeater track relay, a circuit for energizing said repeater track relay including a source of current and a contact of said track relay closed when such track relay assumes one of its two positions, and a circuit for energizing said repeater track repeater relay including a source of current a contact of said track relay closed when it assumes its other position and a second contact of said repeater track relay closed when said rst contact is closed. i

NELSON B. COLEY. 

